Method of forming fastening devices



Aug. 21, 1945. H. w. KOST 2,383,133

METHOD OF FORMING FASTENING DEVIQES Filed Jan. 31, 1942 '2 Sheets-Sheet1 INVENTOR 199M040 W K057 WMQ/QM ATTORNEY Aug. 21, 1945. V H. w. KOST 2,33

METHOD OF FORMING FASTENING DEVICES Filed Jan. 31, 1942 2' Sheets-Sheet2 flczz ald Inf/(m? IN V EN ZOR.

A TTORNEY Patented Aug. 2 1, 1945 Mnrnonor roamso rssrmvnw nnvrcssHarold w. xm'nlmig ham, Mich, assignor to Detroit Harvester Company,Detroit, Mich, a

corporation of Mic Application January 31, 1942, Serial No. 429,330 4Claims. (01. 113-116) This invention relates to fastening devices, and vis particularly directed to a method of forming sheet metal structuresor elements for self docking threaded engagement by a screw. Moreparticularly, the invention is concerned with the production of theself-locking thread and adjacent portions of the structure or element bya'succession of comparatively simple operations or steps.

'An object or the invention is to produce a method of forming aself-locking thread in sheet metal structures-or elements whereby around screw-thread receiving aperture is obtained.

In one aspect this invention provides a method of forming a sheet metalstructure or element for self-locking engagement by a screw in which aportion 01. the metal is pressed out of the normal plane of the sheet toproduce an imperforate substantially frusto-conical protuberance, a holeis pierced in the end wall with the circumferential wall of the holedisposed perpendicular to the plane of the sheet, the protuberance isslit from one edge of the hole to a point adjacent the base of theprotuberance. The metal at one side of the slit is pressed in adirection toward the sheet so that a portion of the wall of the openingis formed into the inner or lower portion of a helix which extendsprogressively anduniformly to the outer or higher portion of the helix.During the final pressing operation, the edge wall of the opening isheld in a positionperpendicular to the sheet.

Further objects and advantages of the inven- .tion reside in the stepsand sequence of steps hereinafter more fully described and for purposesof illustration but not of limitation,-embodiments of the invention areshown on the accompany ing drawings in which a Figure 1 is a perspectiveview of a sheet metal element having a self-locking thread formed inaccordance with the present invention;

Figure 2 is a side elevation of a sheet metal element having aprotuberance formed therein and illustrating the initial step in thepresent method;

Figure 3 is a view similar to Figure 2 and illustrating the second stepof piercing the top of the protuberance;

Figure 4 is a view similar to Figure 2 illustrating the step of radiallyslitting the wall of the protuberance and forming the adjacent edgeportions of the material adjacent the aperture;

Figures 6 and 6 are side elevations of a sheet metal structure adaptedfor the production of the element in accordance with a modified methodconstituting a part of the present invention Figure 7 is a detailedsectional view of the self-locking thread formation shown in thepreceding tlgures with a screw applied thereto:

Figure 8 is a perspective view oi a fastener having upstandinglongitudinal flanges;

Figure 9 is an enlarged longitudinal sectional view of the fastenershown on Figure 8 mounted on a supporting panel and with ascrew appliedthereto; and

Figures 10, 11 and 12 are top plan views showing respectively the stepsemployed in producing a fastener according to Figures 8 and 9.

Referring to Figure 1 of the drawings, a sheet metal element adapted forthreaded engagement by a screw and produced by the method oi the presentinvention has been illustrated in the form of a substantially squarebody II, which is intended to be representative of all structures orelements which are suitable for production in accordance 'with'thepresent invention. It is to be understood that the body I! may take theiorm of a large panel or sheet which has formed therein one or more oithe self-locking thread formations so that the same may be of anydesired shape diii'erent from that disclosed.

The body I! has formed therein a protuberance designated in its entiretyby the numeral II, in the top or apex of which has been pierced a holeor aperture I4 and a radially extending slot or slit ll, which isprovided in the wall of the protuberance, and extends from the edge ofthe aperture II to a point adjacent the base oi the protuberance. Theedge or wall of the opening it is shaped or developed, in the mannerhereinafter appearing and by means or suitable tools. to take the formof a helix 01' a length substantially equal to one convolution of thethread of a screw which is to be associated with the selflocking threadformation. Accordingly, at a point I], which is at the juncture of theaperture and the slot, is provided the high part of the developed helixand at a point II is provided the low part of the helix. The high pointII and the low point ll of the helix are axially spaced a distance equalto the pitch of the thread of the screw, which is to be associated withthe structure or element represented by the member II.

'It is to be understood that many diillculties arise in the productionor a structure such as has been illustrated in Figure 1, and it will beappreciated that the problem of so forming the aperture and adjacentportions of the metal, embraces a number of difllculties in order toproduce a structure that will positively and uniformly engage the innersurface or based a screw thread without detrimental distortion of thestructure I 'or severing of the screw thread upon tightening.

ness of the aperture is maintained. Furthermore,

the diameter of the finished aperture I4 is the same as that of theinitially formed opening. Thus, the forming operation serves to depressthe metal adjacent a portion of the aperture downwardly to complete thelower half of the helix, it being noted that the lowest point of thehelical wall is dispose above the normalplane of the body Ill.

The operations Just described are preferably performed in rapidsuccession by a plurality of is provided with an unperforatedprotuberance l2 having an irregular, generally cone-shaped contour.The'protuberance has a topportion 20 disposed at an angle with respectto the normal planeof the base or body ll providing'at one side thereofthe height or depth required for the high point H, the adjacent wall ofthe protuberance including a smooth curved. lower portion, indicatedgenerally at 22, blending into the body 10 and from which the wall isinclined upwardly in substantially a straight line as at 23, and

slightly inwardly curved as at 24 adjacent the high point II. Theopposite side of the protuberance conforms generally to that portionJust descrew has a head 32 and a threaded body orscribed, but is of alower over-ail height for a purpose hereinafter appearing. Theprotuberance is formed by pressing a portion of the metal out of theplane of the body III with suitably shaped cooperating dies arranged sothat considerably more metal is pressed out of the plane of the bodyIlito produce the high point I] than at the opposite side of theprotuberance, such metal serving to embrace the upper portion of adeveloped helix or opening now to be described.

The protuberance is subsequently pierced or punched to provide anopening or aperture ll disposed at an angle with respect to the plane ofthe body and having parallel or cylindrical edge or wall portionssubstantially perpendicular to the plane of the body, as shown in Figure3. The

hole or opening it is preferably produced by means of a cylindricalpunch so that a perfectly round aperture, as viewed from the topthereof, is provided in the protuberance, spaced a substantial distanceoutwardly from the plane of the body ill. Dueto the slight angularity ofthe top wall 20, however, it is to be noted that opposite walls of theaperture H are disposedat varyingelevations as at 21 and 28, and thatthe intermediatewall 29 takes the form of a portion of a helix. Portion28 is located intermediate the high and low parts of the helix to engagea central portion successively operating dies and punches, though itwill be understood that the several operations may be separatelyperformed. Should it be necessary or advisable, an additional operationof restriking or reforming the developed structure may be performed inorder to insure that no deformation has occurred.

Referringnow to Figure 'l, the structure pro- I .duced in accordancewith the foregoing description is shown in use, and it will be notedthat the body-10 with its protuberance l2'is attached to an element 30by means of a. screw 3|. The

shank 33 provided with a well known form of screw thread havinganguiarly disposed sides 34 and 36 and a. flat root surface 38. The wallof thedeveloped hole crhelix engages substantially an entire convolutionof the thread provided on screw ii, the inner face or base 38 of thethread being in engagement with the opening it uniformly throughout itslength. The cylindrical wall of the opening I4 is flush with the base ofthe screw thread from the extreme upper corner or edge to the extremelower corner or edge. The high point I! of the structure being inturnedby the formation of the wall portion at 24 engages the upper portion ofthe screw thread while the low point it being pressed downwardly andinwardly engages the end of the thread convolution below that of thehigh point ll while the intermediate portion of the helix engages.

the thread of the screw at an intermediate portion thereof. As the screwis tightened down,

of the screw thread convolution, substantially diametrically oppositethe high and low parts thereof. During, the piercing operation thegeneral contour of the initially formed protuberance is maintained sothat the curvature of the wall portions indicated at 22, 23 and 24corresponds to that provided by the initial forming operation, and thehigh point I! is'retained in the same relative position with respect tothe base of the protuberance.

As illustrated in Figure 4, the pierced protuberance is subsequently,provided with a slit at I 6, and the material at one side thereofpressed downwardly so that a portion of the wall of the opening isformed into the lower portion or half of the helix and to position thelow point l8 thereof. It is to be noted that during the. slitting andforming operation the high point ll, as well as the upper portion of thehelix, are maintained in their the protuberance II will be compressed orfiattened to a certain extent with the result thatthe edge wall of theaperture It will be forced.

radially inwardly throughout its length to effect a binding actionagainst the root surface 38 of the screw. The thickness of the sheetmetal body cannot exceed or even be equal to the pitch of the screwthread or the edge of the aperture would bind against the opposed sidesof the screw'thread. Likewise, forming operations cannot alter thethickness of the metal adjacent the opening or a similar result wouldoccur. Therefore, by use of the, foregoing method, the protuberance maybe drawn to a thickness substantially equal to the distance between thethreads of the particularscrew with which the structure is to be used,and subsequent operations-performed without altering such thickness ofmetal.

Referring to Figures 5 and 6, a modified method of adapting the sheetmetal structure or element for the reception of a screw, has beeniiiustrated. In its completed form, the structure same relativepositions and that the edge or wall of the aperture I4. is retainedperpendicular to theplane of the body portion so that the roundis thesame as that shown in Figure l, the steps involved in its productionbeing somewhat modified over those hereinbefore described. First,

the sheet metal is formed with a protuberance 40 of the general form ofthe finished structure and including a radial slit 4!. The next step inthe operation consists in punching or piercing a hole 44 in the top ofthe protuberance and forming the adjacent wall of the protuberance intothe form of a helix having a pitch approximating that of the screw,which the structure is adapted to receive. This latter step ispreferably preformed as a compound operation in orderthat the edge orwall 45 of the opening 44 will be disposed perpendicular to thenormalplane of the sheet, and maintained in that position during'the formation.of the adjacent metal to provide an opening of spiral form. By 'sopunching and forming the opening, it will be clear that the danger ofdeforming the hole is eliminated.

The protuberance initially formed is prefer ably made of a size andshape in which the highest point is equal to the highest point of thefinished structure, the angularity of the walls similar to the finishedwalls, and the base of a di- I ameter equal to that of the finishedbase. it will be noted that the metal required for the finishedstructure is initially drawn out of the plane of the body portion, andsubsequent steps varying thickness as a result of any subsequent drawingor forming operation. As the entire thickness of the protuberance willenter the ,helical groove in the shank of the screw and being uniformthroughout, a thread, strength will be formed.

The preferred operations may take place in rapid succession upon asingle reciprocating movement of a compound die toward a suitablematrix, apart of the die and matrix cooperating to form the protuberanceand slit, to be followed in succession by a punch to form theperforation, and a die to form the wall of the opening to produce thescrew receiving aperture in-helical form. A similar succession offorming and punching operations can be performed in a; progressive die,as will be clearly understood. I The fastener shown on Figures 8 and 9is similar to that hereinbefore described except for the side flangesll. which adapt the fastener for a specific use. Figures 10, 11 and 12show the meth- 0d of forming this fastener. A strip of sheet metal MI isprovidedand from this, a section 49 of the portion 0, a surface (2extends by a gradual curve,

to and merges with the circular portion at the point b. Thus aprotuberance is formed which may be defined as a composite involutecircular protuberance, the circular portion as above indicated extendingfrom the point a to the point b and the involute portion being thecurved portion d which terminates at the inclined notch portion' d. V

In the next operation of forming the fastener as indicated on Figure 11,the protuberance is pierced to provide a hole 5| in the central portionthereof. This hole is formed with a circular portion extending from thepoint a to substantially the point D. From the point 11' extends an in?of great Thus,[

wardly curved surface d" which, as compared with the circular portion orportion of uniform radii a'--b', the curved surface d has decreasingradii. The curved portiond' terminates at a notch portion c which is inthe same general position with respect to the protuberance as the notchc above described. It will be manifest that the shape of the hole 5|resembles that of the base of the protuberance except in reverseposition.

In the next step, the slot 52 is formed which extends from'the point aof the hole Iii-substantially' to the point a at the base of theprotuberance. The side e of the slit is then pressed in a directiontoward the sheet ,49 in such a manner that a portion of the wall of theopening is'formed into the inner portion of a helix. The helix extendsprogressively and uniformlyfto the outer portion 1. The last describedslitting and formingoperations are done by dies and in such a mannerthat the edge wall of the hole it remains unchanged and in position. atapproximately right angles tothe plane of the sheet 49. Preferably theformation of the flanges 4! is accomplished prior to the final formingsteps of the fastener. A fastener produced in accordance with thismethod is particularly adapted for use in connection with heavier gaugemetal and the fastener can I be very satisfactorily produced toaccommodate a screw formed with an acme thread.

This application constitutes a continuation in part of my applicationSerial No. 264,956 filed March 30, 1939, and entitled Method of formingfastening devices."

It is to be understood thatnumerous changes in'detailsof construction,arrangement and operation may be effected without departing from thespirit of the invention especially as defined in the appended claims.

What I claim is:

1. The method of forming a sheet metal structure or element forself-lockingengagement by a screw comprising pressing a portion of themetal out of the normal plane of the sheet to produce an imperforatesubstantially frusto conical protuberance with an end wall inclinedlydisposed relative to the plane of the sheet. and side wallscircumferential wall thereof disposed perpendicular to the plane of thesheet, radially slitting the protuberance from one edge of the hole atthe highest point of the protuberance and in a direcinto the inner orlower portion of a helix which extends progressively and uniformly tothe outer an imperforate substantially frusto-conical protuberance withan end wall inclinedly disposed relative to the plane of thesheet andside walls inclining gradually from the end wall to the sheet, piercinga round hole in said end wall with the circumferential wall thereofdisposed perpendicular to the plane of the Sheet, radially slitting theprotuberance from one edge of the hole at the highest point of theprotuberance and in a direction radially thereof to a point adjacent thebase of the protuberance, pressing the metal at one side of the slit ina direction toward the sheet so that a portion of the wall of theopening is formed into the inner or lower portion of a helix whichextends progressively and uniformly to the outer or higher portion ofthe helix, holding the edge wall of the opening perpendicular to thesheet during said last pressing operation, and restriking the developedstructure to insure against deformation.

3. The method of forming a sheet metal structure or elementforself-locking engagement by a screw comprising pressing a portion ofthe metal out of th normal plane of the sheet to produce an imperforatesubstantially frusto-conical protuberance with an end wall inclinedlydisposed relative to the plane of the sheet and side walls inclininggradually from the end wall to the sheet, piercing a hole in said endwall with the circumferential end wall thereof disposed perpendicular tothe plane of the sheet, said hole being round except for a notch and aninvolute curved edge portion contiguous thereto, and thereafter slittingthe metal from said notch to the base of the protuberance and pressingthe metal at one side of the slit in a direction toward the sheet sothat a portion of the wall of the opening is formed into the inner orlower portion of a helix which extends progressively and uniformly tothe outer or higher portion of the helix, and during said last stepholding the edge wall of the opening perpendicular to the sheet.

4. The method of forming a sheet metal structure or element forself-locking engagement by a screw comprising pressing a portion of themetal out of the normal plane of the sheet to produce an imperforatesubstantially frusto-conical protuberance, piercing-a hole in said endwall with the circumferential end wall thereof disposed perpendicular tthe plane of the sheet, said hole being round except for a notch and aninvolute curved edge portion contiguous thereto, and thereafter slittingthe metal from said notch to the base of the protuberance and pressingthe metal at one side of the slit in a direction toward the sheet sothat a portion of the wall of the opening is formed into the inner orlower portion of a helix which extends progressively and uniformly tothe outer or higher portion of the helix, during said last step holdingthe edge wall of the opening perpendicular to the sheet, andsubsequently restriking the developed structure to insure againstdeformation and to press the edge wall of the hole into a planesubstantially parallel with the sheet and to make the extreme edgeslightly thinner than the remainder, thereby to provide a portion forengaging substantially between the threads of a screw.

' HAROLD W. KOST.

